1. Field of the Invention
The present invention relates to an optical storage apparatus. More particularly, the present invention relates to a method for automatically adjusting a loop gain of an optical storage apparatus.
2. Description of Related Art
Generally, when a compact disk (CD) is rotated, it may have a vertical and a horizontal radial wobble. Therefore, to maintain the quality of read or write data, and to keep a good response value, an optical storage apparatus can correct gains of a track loop and a focus loop in a servo control loop. Regarding a re-writable compact disk (CD-RW or DVD-RW), when the disk is played, the optical storage apparatus can correct the loop gain of the servo control loop through a read power. When a write operation is performed, the optical storage apparatus can adjust the loop gain according to a ratio between an erase power and the read power.
However, in case of the same erase power, regarding the disks having different reflectance, an error signal obtained by the optical storage apparatus is unnecessarily to be proportional to the erase power. If the loop gain is adjusted according to the ratio between the erase power and the read power, a servo signal and a wobble signal are deviated from their optimal values, which may result in a fact that the loop gain is deviated from its optimal value or the wobble signal exceeds an input range of the servo control loop.
Generally, when the servo loop gain is deviated from its optimal value, a bandwidth of the servo is changed, or stability of the servo is decreased, which may finally lead to a decrease of a write quality or lead to a write failure. Similarly, when the wobble signal exceeds the input range of the servo control loop, a wobble signal quality is decreased, so that jitter amounts of a wobble clock and a write clock are increased, which may also lead to a decrease of the write quality or lead to the write failure.
To resolve the above problem, when an offline test of the optical storage apparatus is performed, an optimal loop gain can be designed to each of the disks. However, since types of the disk are diversified, if the loop gains of the disks are respectively designed, the huge amount of data can lead to excessive data searching time. Moreover, as the disk technique is continually developed, when a novel disk is presented, data update thereof has to be performed, which can increase a complexity of a follow-up processing.